1. Field of the Invention
This invention relates to a method for fabricating a resist pattern, a method for patterning a thin film and a method for manufacturing a micro device.
2. Related Art Statement
Thin film-patterning is performed by using a milling method, a lift-off method or a combination method of milling and lift-off. As a resist pattern for the thin film-patterning, is employed a two-layered structure, that is, a Bi-layered type resist pattern which includes a photoresist layer as a top layer and a polymethylglutarimide layer (PMGI layer) as a bottom layer.
FIGS. 1-5 are cross sectional views showing the fabricating steps of the Bi-layered type resist pattern.
First of all, as shown in FIG. 1, a PMGI layer 3 is coated on a given base material 1 and heated as occasion demands. Then, as shown in FIG. 2, a photoresist layer 5 is coated on the PMGI layer 3, and heated as occasion demands. Thereafter, as shown in FIG. 3, the photoresist layer 5 is exposed via a given mask 7 through UV irradiation.
Thereafter, the exposed photoresist layer 5 is developed, and the remaining PMGI layer 3 is partially removed with an alkaline water solution, to form a resist pattern 9 as shown in FIG. 4 or a resist pattern 10 as shown in FIG. 10.
The main body 9-1 of the resist pattern 9 is made of the photoresist layer 5, and the supplemental body 9-2 thereof is made of the PMGI layer 3 and narrowed as compared with the main body 9-1. Similarly, the main body 10-1 of the resist pattern 10 is made of the photoresist layer 5, and the supplemental body 10-2 thereof is made of the PMGI layer 3.
In the case of patterning a thin film via the resist pattern 9 as shown in FIG. 4 by a milling method, a large amount of milled wastage may be stuck on the side surface walls of the supplemental body 9-2. Therefore, in the dissolving and solving step for the resist pattern 9, the penetration of solvent is blocked due to the stuck wastage of milling, and thus, the resist pattern 9 may not be perfectly dissolved and removed.
Moreover, if the bottom portion of the supplemental body 9-2 is enlarged in its width due to the stuck wastage of milling, the patterning condition of the thin film is affected.
Moreover, in the resist pattern 10 as shown in FIG. 5, the main body 10-1 can not be supported by the supplemental body 10-2, so that the main body 10-1 may come off in patterning a thin film.
It is an object of the present invention to provide a method for fabricating a resist pattern without the above-mentioned defects, and to provide a method for patterning a thin film and a method for manufacturing a micro device which uses a resist pattern obtained through the fabricating method.
In order to achieve the above object, this invention relates to A method for fabricating a resist pattern having a T-shaped longitudinal cross section which is constructed of a main body having a substantially rectangular longitudinal cross section and a supplemental body to support the main body on a given base material and having a substantially rectangular longitudinal cross section narrowed as compared with the longitudinal cross section of the main body, including the steps of forming a polymethylglutarimide layer on a given base material, washing the surface of the polymethylglutarimide layer with an organic solvent, forming a photoresist layer on the polymethylglutarimide layer, exposing and developing the photoresist layer via a given mask, and partially removing the remaining polymethylglutarinide layer with an alkaline water solution, to form the resist pattern.
The inventor had intensely studied to prevent milled wastage from sticking on the side surface walls of the supplemental body of a resist pattern. Then, the inventor found out that the sticking of the milled wastage results from the configuration of the supplemental body, that is, the tapered supplemental bodies 9-2 and 10-2 as shown in FIGS. 4 and 5. Therefore, the inventor had conceived to make vertical the side surface walls of the supplemental body.
The upper region of a PMGI layer can not be thermally polymerized sufficiently, so may be dissolved and removed at higher velocity than the lower region thereof because the dissolution velocity of the un-polymerized region is larger than that of a polymerized region. As a result, the supplemental body made of the PMGI layer is tapered as shown in FIGS. 4 and 5.
In thin point of view, the inventor had conceived to remove the upper region of the PMGI layer beforehand which is not polymerized sufficiently, to make uniform the dissolution velocity of the whole of the PMGI layer. That is, according to the present invention, after a PMGI layer is formed on a given base material, the surface of the PMGI layer is washed by an organic solvent, to remove the un-polymerized region. As a result, the dissolution velocity of the PMGI layer for a developing solution can be made uniform entirely, to make vertical the side surface walls of the supplemental body of the thus obtained resist pattern.
A method for patterning a thin film according to the present invention is characterized by using a resist pattern obtained through the fabricating method of the present invention as mentioned above.
Moreover, a method for manufacturing a micro device according to the present invention is characterized by using the patterning method of the present invention as mentioned above.
In the present invention, the wording xe2x80x9cgiven base materialxe2x80x9d means a single substrate or a combination of a substrate and an underlayer for a thin film to be milled or a micro device.